Automatic steering apparatus



J y 28, 1953 R. .,I. KUTZLER 2,647,233

AUTOMATIC STEERING APPARATUS Filed April 16, 1949 r 1 7/ E. 32 I I5 II I 28 I6 AMP SERVO-"1*"- 27 I0 AUTO ILOT AMPLIFIER INPUT NETWORK I RATE TURNS HEADING AND STABILIZING AMP l6l VELOCITY GENERATOR GYRO STABILIZED I34 MAGNETIC p I23 Ill "5 I93 COMPASS I35 L "4 r |30 \1 n L 1 I33 I26 I95 I20 93 I '7 "6 /99 I02 a I05 INVENTOR. l

fig)? I06 Id ROBERT J. KUTZLER SERVO: AMP l BY l ZZ I00 I04 03 16 A 7' TORNE Y Patented July 28, 1953 UNITED STATES PATENT OFFICE AUTOMATIC STEERING APPARATUS Robert J. Kutzler, Minneapolis, Minn., assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application April 16, 1949, Serial No. 87,909

4 Claims. 1

This invention pertains to direction maintaining apparatus for dirigible craft such as aircraft, water craft, and the like. This invention more particularly concerns direction maintaining means which may be utilized to control automatic steering apparatus for dirigible craft.

An object of this invention is to provide a direction maintaining apparatus in which an indicator is controlled by a free gyroscope and a magnetic compass and in which the primary operation of the indicator is derived from the gyroscope with means for correcting the position of the indicator by readjusting the same with respect to the gyroscope in response to deviation in relative position of said compass and gyroscope.

It is a further object of this invention to provide an epicyclic gear train between an indicator and a directional gyroscope in such manner that the fixed axis of the gear train is co-linear with the axis of the indicator and of the gyros-cope and wherein the movable axis of said gear train is operated in accordance with change in relative position of said gyroscope and a magnetic compass.

It is a further object of this invention to utilize th means for positioning said indicator for adjusting the controller of an automatic steering mechanism to maintain a craft on a magnetic heading.

It is a further object of this invention to provide means for readjusting the controller in order to change the magnetic heading on which the craft is to be maintained.

It is a further object of this invention to provide an automatic steering mechanism for dirigible craft which is controlled by a potentiometric controller providing continuous control and wherein said controller is primarily adjusted by a free directional gyroscope, said controller being subsequently readjusted by means under the control of a magnetic compass so that the magnetic heading is maintained. Additional means are provided in said steering mechanism to alter the magnetic heading to be maintained in selected angular amounts and alternatively to alter the magnetic heading to be maintained at a selected angular rate.

The above and further objects and novel features of the invention will more fully appear from a consideration of the detailed description when the latter is read in connection with the accompanying drawing.

In the drawing wherein lik referen ch acters refer to like par 1 Figure 1 is a diagrammatic representation of one form of the novel apparatus embodying the present invention; and

Figure 2 is a diagrammatic representation of a second form of the novel apparatus embodying the present invention.

Referring'now to Figure 1 of the drawing for a more detailed description of the automatic steering mechanism of the present invention, a control surface (not shown) for controlling the direction in azimuth of a dirigible craft is operated from a servomotor ID. The servomotor I0 is reversibly controlled by an amplifier The amplifier-servomotor combination may be of the type well known in the art wherein the direction of rotation of the servomotor depends upon the phase relationship of the voltage across power input terminals l3, I4 of amplifier II with respect to the voltage across the signal input terminal connections I5, l6 of amplifier II. The amplifier-servomotor combination may be of the type disclosed in United States Patent 2,425,734 of W. H. Gille et al.

The signal input connections l5, I6 of amplifier II are included in a variable impedance circuit which additionally comprises impedance network |8, lead 29, autopilot amplifier input net- Work 30, and lead 33vwhich is common to amplifier ground connection I6.

The variable impedance network l8 consists of a directional control potentiometer l9 having a resistor 20, a slider 2| coacting with the resistor and a transformer 22 having a primary winding 23 connected to the ships supply and a secondary winding 24. The resistor 20 is connected across the ends of secondary winding 24 of transformer 22. Connection [5 extends from amplifier II to a center tap 25 of secondary winding 24. The resistor 20 is supported by a gear member 26 which in turn (by means not shown) is rotatably carried by the craft. The gear 26 meshes with a pinion 21 which may be operated by a coursechanger 28. The slider 2| is stabilized on a given direction by means to be described.

It will be appreciated that with the network l8 mounted on a craft with the slider 2| at the mid point of resistor 20 the potential of wiper 2| is the same as that of center tap 25 of secondary winding 24. Itwill also be apparent that if the resistor 20 is moved with respect to the stabilized slider 2| either by movement of the craft or by adjustment of the gear 26 by the course changer 28 that the slider 2| and center tap 25 are at difierent potentials. Moreover, the direction or phase of this potential difierence will depend upon the direction of displacement of resistor with respect to slider 2!. This potential difference between slider 2i and center tap constitutes an electrical signal and the potentiometer l9 constitutes a signal generator or pick-off responsive to changes in direction of the craft or to operation of the course changer.

The input network So may be an elaborate network of series connected variable potentiometers such as disclosed in my application Ser. No. 22,841, filed April 23, 1948. However, for facilitating the understanding of the invention, the networl; 36 may be considered analogous to the potentiometer it of Patent 2,425,734 mentioned above. The network is operated by a follow-up connection 32 extending from the servomotor ii! analogous to the operation of the follow-up potentiometer iii of the aforesaid patent. A lead 29 extends from the slider 2! of potentiometer iii to the input network 39. A lead extends from the network 3a to ground which is common with the grounded lead lo of amplifier H.

The stabilizing apparatus consists of a magnetic compass 35, an electrical differential or position comparing device 36 consisting of a magnetic compass position potentiometer 31, and a gyro stabilized resolver or follow-up potentiometer =1 a directional gyro M, an epicyclic gear train of, an error signal reducing motor 65, and an error signal responsive amplifier 55. The compass position potentiometer 3'! consists of a circular resistance unit 38 and a double contact arm 39, which engages the resistance unit. The douole contact arm is positioned by a standard compass to assume a position according to the position of the compass needle 34. The end portions of the double contact arm 39 are suitably insulated from the positioning means by insulating segments is. The double contact arm may be connected to a source of alternating voltage which may be the ships supply. Leads 4 I, 42 and is which extend from equal angularly spaced points of resistor unit 38 are connected to corresponding points of resistor unit 45 of the followup potentiometer M. A double contact arm 48 coacts with the resistor unit 45 or potentiometer A vertical shaft 38 extends from the center or double contact arm as and is connected to the slider 22! of potentiometer E9. An extension 49 of one end of the double contact arm 45 serves as an index which coacts with a magnetic heading dial 5% bearing suitable indicia 5|. The ends of the double contact arm which bear on the resistor and which are insulated from the shaft 58 by suitable insulating segments 52 are connected respectively by leads 53 and 54 to the position error amplifier 55.

The amplifier is of the A. C. discriminator type and has power input connections 58, 51 connected by leads 59 to the ships supply. Output connections 5? 6! of amplifier 55 are connected to one phase winding of a capacitor type induction motor 54. The other phase winding of the motor B lis connected by suitable leads 6!, 83 to the supply leads 58, 59. The motor 64 is reversibly controlled by the amplifier 55 in accordance with the phase relationship of the voltage across the signal input terminals of amplifier 55 with respect to the voltage of the ships supply. Such amplifier-capacitor motor combinations are old in the art, an example being disclosed in the patent to Beers, 2,020,275.

The motor 65 drives through a suitable reduction gearing (not shown), a worm 65 which meshes with a worm gear 65. The gear 65 is secured to a shaft 61 which drives the double contactor 46 of potentiometer 44. The shafts B1 and 48 are coaxial.

The motor 64 is carried by a turntable 68 supported by bearing means 69 on a base '50. The turntable 68 is operatively driven through a coupling H from a trunnion 12 of the vertical gimbal ring 13 of a directional gyro M. A lower trunnion 78 of the gimbal ring 1'3 is suitably supported in a bearing 15. The directional gyro W- includes a rotor, not shown, carried on a horizontal spin axis in a casing H. The casing ll in turn is carried by trunnions l8 and 39 in the vertical gimbal ring 13. The axis of trunnions l3, "i3 is horizontal and at right angles to the spin axis of the yro rotor. The arrangement is such that the axis of rotation of the trunnions i2, '56 of the vertical gimbal ring 73 of gyro M, the turntable 68, and the gear 56 are colinear.

Considering now the operation of the arrangement described and shown in Figure 1, the double arm contactor 45 of potentiometer 44 must assume a position at right angles to the position of the double contact arm 39 of potentiometer 38 in order that there be no diiierence of potential across the leads 53 and 54.

Automatic steering or stabilized course control is provided by the directional gyro M. This occurs in the following manner. Assuming that the craft is on a selected course with the slider 2| at the mid point of its resistor 26, the input circuit of amplifier i I may be assumed in balanced condition with the servo balance potentiometer included in network 30 at balance. If the dirigihis craft swings off its heading, the gear 26 car ried by the craft rotates with respect to the stabilized slider 2|. The slider 21 is maintained in space by the directional gyro '56 through the turntable 58, the gear train 4?, and the shafts 61 and ca. The displacement of resistor 25 with respect to slider 2| sets up a difference of potential between slider 2i and the center tap 25 of secondary winding 24 resulting in an unbalance in the input circuit of amplifier i i. The amplifier l i causes the operation of the servomotor l5 which positions the course control surface in a manner to return the craft to the stabilized heading. As the craft approaches the stabilized heading, the amount of control surface displacement decreases until on attainin the desired heading the control surface is again centered. Th index 49 indicates on dial 511 the deviation of the craft from magnetic heading desired.

Over a period of time, the directional ro 14 tends to wander from its original position. In such circumstance, the heading of the craft would change to follow the wandering of the gyroscope 14. To permit the free gyroscope '14 to wander and yet to prevent such wandering to be reflected in the positioning of the slider 21 is the function of the magnetic compass 35 and the electrical difiierential 35.

With the double contact arm 46 in the null or no signal position with respect to the position of contactor 35, the signal input leads 53, 54 of amplifier 55 are at the same potential. If the gyroscope 74 tends to wander, it will through the turntables 68 and gear train 4'! displace the contactor 4G and the slider 2|. The contactor 46 has now been displaced from null position with respect to contactor 39, and a voltage is applied across the input terminals of amplifier 55. The amplifier 55 causes the operation of the capacitor motor 64, The pinion 65 driven by the respect to the indicating dial xscope I4ispermitted to assume a new position Figure l. the coursecontrol potentiometer 9d having a cirdriving gear It'll. signal generator or course control pick-cit. Such motor 64 is 'the'member of the epicyclic gear trainfllwhose axis of rotationxis movable about two axes. It rotates gear I55 and contactor -46'ito .a null position. At this time the inputtcircuit of serrorisignai amplifier 55 is in balanced condition [and the operation of motor'ES-i stops. tioning ofrthe contactor ill has also repositioned the slider 2I with respect to the free gyroscope The posi- I4 and'has also repositioned the index 48 with Thus the gyrowith respect to the slider 2| and index 49 whereby ltheioriginal course of the craft is maintained and indicated.

While the motor 6d and its pinion 85 are responsive "to changes in relative position of the ."magnetic "compass. 35 and the directional gyro 14 due to wandering of the gyroscope, thetemporacy deviations of alignment of gyroscope and compass 35 due to oscillations i the compass are not corrected by the motor i s due to the slow response of its output gear I35 to such temporary deviation signals.

Reference isrnade to Figure 2 in conjunction with the following detailed description of a second-formof the invention. In Figure 2, a servomotor 90 operates the control surface of the craft .to maintain or change the heading to be maintained. The servomotor is reversibly controlled by an amplifier ill. The servomotor lid and amplifier 9| are similar to the amplifier Ii and servomotor IQ of Figure l.

The signal input circuit or amplifier ll I includes .a variable impedance network 533 corresponding with network It of Figure 1 and input network I It corresponding with the network 30 of The impedance network 38 includes cular resistor [til and a slider Iill contacting the same.

supply. A center tap loll of secondary winding I04 is connected to ground which is common to the ground connection of a signal input connection of amplifier c i.

The slider Elli is stabilized by a free directional gyroscope I i l similar to the directional gyroscope M of Figure 1. To this end. the slider 'IBI is secured to the lower trunnion l Ill of the outer girnbal ring of the vertical gyro i it.

The upper trunnion iII of the outer gimbal ring'is suitably journaled in bearing H5. The supporting bearing for lower trunnion Md has been omitted for clearness.

The resistor tilt! is carried by a gear member 06. The gear member lilli is in mesh with a The networksii constitutes a signals are obtained by relative displacement of the'slider ID! with respect to the resistor lilo.

"Forthe usual stabilizing on a given heading by "thegyro H4, the resistor'ltd is not displacedwith respect to the craft. The resistor Iilil maybe displaced with respect to the craft byoperation The resistor Ito is connected across a secondary winding W4 01' a transformer H32 having aprimary winding ltt conn cted to the ships H16. changes of selected angular amounts, and changes inheadingat selected rate are secured by operof gear I01, in mesh with resistor supporting gear Correction "of a gyro heading, course ating gear 101. Forsuch operations, 'thegear 'Ill'I is carried'bythe output shaft I20 ofacapaci- :tor type induction motorPI2 I'which is hereinafter upon the phase relationship between the voltage across the input connections I34, I35 and'that across the supply leads I 25, I26.

The signal inputconnections I34, N5 of amplifier'l'22 are in series with the output of a velocity generator I 36 and through a three position'switch I49 to a source of'voltageto be described. The operation ofthe amplifier, velocity generator and steering motor is such that when an'initiating control signalof a particular value is applied to the amplifier I22 the steeringm'otorIZI operates. The motor I2 I drives the velocity generator I 36 so as to generate a voltage which opposesthe control voltage. Ultimately therefore the motor -I2I attains a speed dependent upon the amountof'control voltage initially applied. The steering motor, amplifier, velocity-generator combination maybe similar tothat-disclosed in the aforesaid applicationSer. No. 22,841.

The various means for providing'a signal for initiating the operation o'f'amplifier I22 will be described. Turns at selected rates are initiated from a rate turn knob I44 which adjusts a slider 'I 45 of a rate turn potentiometer I46 with respect to theresis'tor 'I4'I. A lead I46 extends fromthe slider I45 to the upper contact of switch 140. The resistorl 4'I of'potentiometer I46 is connected across a secondary winding I63 of atransformer I64, the winding I63 having a grounded center tap. The secondary of such transformer may be energized by a primary winding I 03 which may be common to transformers I62, 'IM'andIIiB.

Changes'in'heading-in selected angular-amounts is controlledby a course turn knob 'I 50. The knob I50 is carried by an axially slidable shaft I5I which supportsat its opposite end a gear I52. The shaftI5I is carried ina bracket I57. When moved toward the left a stop I59 on shaft -I5I engages the bracket I51. A similar stop (not shown) may be provided for'lim'iting the rightward movement of the shaft. In its right position, the pinion I52 on shaft I5I meshes with a geari53. The

-gearl 53supports a resistor I54 of a course change potentiometer I523. The slider I55 of the course change potentiometer is mounted on an extended continuous shaft I60. A biasing or centering spring i 55 is secured to the slider I55 at one end and to the gear I53 at theother end. When the gears I52and I53 are demeshedthe springcenters the resistor and .slider. The resistor IE4 is connected across a grounded center tapped'secondary winding I of a transformer I65.

Any voltage signal developed in potentiometer I553 is applied-to a discriminator limit amplifier IEI. The amplifier I6I may be'similar toamplifier I58 of sapplicationSer. No. 22,8 l1. "Such 'amplifier ISI as is also'disclosed in the aforesaid application :provides an output voltage: of .fixed.

connections I 18, I19.

*value "but-iof ipositive or negative value with respect to ground depending on the phase of the input signa-lwappliedthereto. The output voltage -ofampli'fier I-6I is transmitted by lead I62 which corresponds with lead 258 of the aforesaid application. Lead I62 extends from amplifier I6I to thelower'contactofthe three position switch-I40.

Reverting to the continuous shaft I60 which supports theslider I55 of potentiometer I56, this shaft isdriven'by'a capacitor type induction motor I10. Onephase winding of the motor I10 is 'connectedby leads I11, I12 to the ships supply line. The otheriphase winding of motor I10 is connectedacrossthe output of a magnetic course amplifier Iby leads I13, I14. Amplifier I15 has power-inputleadsflB, I11 extending to the ships The amplifier I15 includes signal input The shaft I60 carries a rotorof a velocity-generator I80 and the rotor of a resolver or follow up potentiometer I8I. The

supply.

shaft I60furthercarries a pointer I82 which coacts with-an indicia bearing magnetic heading dial-I83.

Returning-to a further discussion of the amplifier I15, theamplifier, like amplifiers 55, I22 is of the known A. C. discriminator type having two alternatively operable tubes in its output stage.

The voltage across the output connections I13,

I14 of amplifier I15 is either in phase with the line voltage across-connections I16, I11 or one half cycle out of phase depending on which tube within the amplifier operates. The current through-the-amplifier phase winding of motor I10 therefore will either lag the line voltage by one quarter'cycle when the signal is in phase with the line voltage or lead the line voltage one quarter'cycle when the signal is out of phase. The line .phase winding'of motor I10 has a condenser in series amplifier winding with respect to the current in theline winding which lag or lead controls the direction of rotation of-motor I10.

The signal input terminals I18, I19 of amplifierI'IS are included in an input circuit which includes the secondary winding of a velocity generator I80and the rotor of a resolver I8I which additionally furnishes a control voltage. The output voltages of the velocity generator I80 and the resolver I9I are algebraically added and applied to the amplifier connections I18, I19 so as to reduce any tendency of the motor I10 to hunt.

The velocity generator I80 is similar to the velocity generator I36 having a secondary winding forming the output member which although stationary is associated with a stationary primary winding by a rotor.

The resolver I8I or follow up potentiometer is similarto the follow up potentiometer 44 of Figure 1. The output connections I84, I85 of potentiometer I8I correspond with the connection 53 and 54 of Figure l. The resistor unit (not shown) of potentiometer I8I is associated by way of leads I86, I81, I68 with a corresponding resistor unit of a compass operated potentiometer. The double arm contactor (not shown) of such compass potentiometer is connected by leads I90, -I9I to theships supply.

It-is to be understood that a magnetic compass corresponding with compass 35 of Figure 1 and a magnetic compass operated potentiometer are contained within the casing I89.

The compass-potentiometer casing I89 is supported on'a rotor casing I of aknown vertical gyro I9I. The casing I90 supports a rotor (not shown) for rotation about a vertical axis. The casing in turn iscarried by trunnions I92, I93 in a horizontal gimbal ring I94. The gimbal ring I94 in turn issupported on a horizontal axis by bearing blocks I95, I96 at an angle perpendicular to the axis of trunnions I92, I93. The axis of trunnions I92, I93 and that of the gimbal ring I94 in blocks I95, I96 are horizontal and at right angles to the'spin axis of the rotor within casing I90.

The mounting of the magnetic compass and its I potentiometer on the vertical gyro I9I will be referred to briefly. It is well known that in order for a magnetic compass to be accurate it should respond only to the horizontal component of the earths magnetic field. However, if the compass should become tilted in any way, it is aifected not only by'the horizontal field but also by the vertical component of the earths magnetic field. To avoid subjecting the compass to the vertical component of the earths magnetic field, the compass has been mounted upon the gyroscope I9I. The gyroscope is provided with conventional means not shown to maintain its rotor in avertical position with respect to the earth consequently it will be readily apparent that regardless of pitch or roll of the craft the gyroscope and thus the compass will be maintained stable about a true vertical. Thus the magnetic compass will be subject only to the operation of the horizontal component of the earths magnetic field and magnetic errors will not be applied to the compass.

The operation of the arrangement shown in Figure 2 will now be considered. It is apparent with the switch in the mid position shown, the input circuit of amplifier I22 is not completed therefore the steering motor I2I is not operated. The free gyroscope II 4 controls the position of the slider I 0| of potentiometer '99. The craft is stabilized on the heading determined by the position of the gyro.

If gyro stabilizing with additionally magnetic compass supervision be desired, the three position switch I40 is moved to the down position. The gyroscope '4 through the controller 99 controls the operation of the steering mechanism motor 90 through amplifier 9|.

Should the gyroscope wander over a period of time, it will operate the slider IOI with respect to resistor I00 and therefore cause the craft to deviate from the magnetic heading on which it is desired that the craft be stabilized. The compass within casing I89 in response to change of heading displaces its contactor relative to its resistor consequently the contactor operated by the magnetic compass is not in a position corresponding with the contactor of the resolver I8I. A signal is obtained from resolver I8I which is applied to the amplifier I15. The amplifier I15 operates the motor I10 which through its shaft I50 drives the velocity generator and the contactor of resolver I8I to a null position.

Movement of the shaft I60 also positions the pointer I 82 to indicate the new magnetic heading of the craft and also positions the slider I55 of operation of steering motor I2I which through earing I07, I06 moves the resistor I with respect to the slider IUI. At the same time the steering motor I2I drives the velocity generator I 36 which develops a signal which is algebraically added to the signal from amplifier IBI. The steering motor I2I therefore rotates at a speed determined by the magnitude of the fixed signal from amplifier I6I. I

The movement given to the resistor I00 by steering motor I2I is in such direction as to cause the craft to return to the magnetic heading de-' sired. As the craft returns to the desired magnetic heading the relative positions of the mag netic compass operated potentiometer and the follower or resolver potentiometer I8I is altered whereby an opposing signal is applied to the amplifier I'I5. The amplifier I75 now causes the operation of motor I in an oppositedirection thereby moving the slider I55 of potentiometer I58 back toward its normal position on resistor I54 thtm stopping operation of amplifiers I'6I, I22 and steering motor liil. As the craft moves back toward the original magnetic heading the index 502 moves back over the dial I83 toward the desired magnetic heading. Upon the attainment of the desired magnetic heading the potentiometer I58 is in balanced condition and the index I32 is pointing to the original magnetic heading with the resolver and magnetic compass operated Potentiometers in corresponding positions. The slider II is at the center of resistor I00 which has changed its position with respect to the craft.

If a change of heading of selected angular value be desired, the course turn knob I50 is rotated in accordance with the amount of turn to be made. The rotation of knob I50 rotates the gears I52 and I53 and displaces the resistor I54 carried by gear I53 with respect to slider I55. A signal from potentiometer I55 is applied to the limit amplifier I6 I. The operation of amplifier It! applies a fixed signal through lead I52 and the three position switch I40 to the amplifier I22 in a circuit including the output winding or secondary winding of velocity generator I36. The motor I2I now rotates and through gearing I 01, I as displaces the resistor I00 with respect to the slider I0l. A signal from the course control potentiometer 09 is applied to the autopilot amplifier 0i which causes the servomotor 90 to operate and position the control surface;

As the craft changes its heading, the compass operates potentiometer and the follow up potentiometer Iti are relatively displaced from a null position, and a signal is applied to the amplifier I15. The amplifier I causes operation of the motor H0 which restores the resolver to a null position with respect to its control potentiometer. Ihe motor I10 also positions the index I82 in accordance with the change in magnetic heading to be made. The motor I10 drives the slider I55 toward the center position of resistor E50.

As the craft changes its heading, it carries with it the resistor I00 which now moves with respect to slider l0I in an opposite direction to that imposed upon it by rotation of motor I2If. This causes an unbalance in the input circuit of the autopilot amplifier 01 whereby the control sur-' face is moved back toward normal position. When the craft has changed its heading in accordance with the amount set up on the turn knob I50, the slider IOI is atthe center of resistor I00 and the resolver or follower potentiometer I8I is in 10 a null position with respect to the magnetic compass operated potentiometer. Also the potentiometer I58 is in balanced condition.

When selected rate turns are to be made the three position switch I40 is moved to the upper position in the figure. The control knob I50 along with its gear I52 is moved inwardly or leftward to disengage gears I52 and I53. If there existed any relative displacement of resistors I50 and I55 the centering spring I56 removes such difference in position. The rate turn knob I44 is now rotated in either direction and to an extent depending upon the direction and the rate of turn to be maintained. The signal from the rate turn potentiometer I08 is applied through the three position switch Mil to the steering motor amplifier I22. The steering motor IZI in response to the operation of the amplifier I22 drives the. gear I01 and through gear I06 the resistor I00 of potentiometer so. The steering motor I2I drives its velocity generator whose output winding or secondary Winding is in series with the signal from the rate turn potentiometer I06. The signals are algebraically added an plied to the amplifier I 22 whereby the speed otation of motor IZI is determined by the signal provided by the rate turn potentiometer I05. 7

The resistor :se is rotated inone direction by motor I2! to displace it wi-t' respect to the gyro stabilized Wiper Ifil. Tha -turning of the plane resulting from the operation of the servoinotor 00' and amplifier iii in response to the initial rela-. tive movement 01" slider Isl and the resistor I00 is in an opposite direction. Should the motor I2! tend to increase the displacement or" resistor ltd with respect to slider IOI the rate of turn of the craft will increase, accordingly and tend to prevent such increase in displacement. Consequently the craft will rotate or cha ng e head-i ing 'at a rate determined by the amountpi signal obtained from the rate of turn potentiometer I46.

Due to the changes in heading of the craft there is a displacement between the compass and the craft consequently the magnetic compass operates its potentiometer so that the respective contactors of the follow up potentiometer IBI and the compass operated potentiometer are displaced from a null position. A signal from the follow up potentiometer or resolver I8I is thus applied to the amplifier Illi causing the operation of motor I10. The motor I'm will drive the index I82 at a rate dependent upon the rate of change of heading of the craft and will drive the contactor of follow up potentiometer I8I to null position. Due to the continuous change in heading of the craft the motor H0 continuously drives its index I32. The slider I55 and resistor I50 of potentiometer E58 are maintained centered with respect to each other by the spring means I50.

As the craft approaches the desired heading to be maintained, the rate turn knob M4 is moved back toward center position on resistor I01. The signal on amplifier I22 therefore decreases and the motor HI stops rotating. The motor In no long-er'rotates the resistor Ilitl with respect to its slider Kill.

Originally it'was stated that the motor I2I positioned the resistor 5th with respect to the slider I0! to initiate the turn of the craft. With the motor I'ZI at this time no longer rotating the turn of the craft is in such direction as to move the resistor lilllwith' respect to slider liil oppo sitely to that provided by the initial operation of motor'ItI'. Consequently the input circuit of the amplifier 9! is unbalanced in an opposite direction resulting in the movement of the control surface by the servomotor 90 back to its normal position or streamlined position.

As the control surface is moved back toward streamline position, the aircraft steadies on the new magnetic heading. The index I82 has been positioned with respect to its dial I83 by the motor Ill! to correspond with the new magnetic heading. The resolver I8! is in a null position with respect to the magnetic compass operated potentiometer. The course turn knob l 50 may be moved toward the right to engage the gears I52 and 553 for any subsequent operation.

While onl two structures embodying the present invention have been shown in the drawings, it is to be understood that various changes may be made in these structures without departing from the scope of the present invention. Therefore, it is intended not to limit the invention by the description herein given, but solely by the scope of the following claims.

What is claimed is:

1. Steering apparatus for a dirigible craft having power means for reversibly actuating a control surface on said craft for changing its heading, said apparatus comprising: an electronic amplifier having its output connected to said power means for controlling the direction of rotation of said power means; a balanceable control circuit connected to the input of said amplifier including a potentiometer having a slider part and resistor part relatively displaceable from a null position; a free directional gyroscope means for adjusting one part of said ptenti ometer; means for adjusting the other part of said potentiometer; a compass reponsive to the earths magnetic field; and means controlled by said compass and effective upon relative movement of said craft and compass for operating the other part adjusting means for stabilizing the heading of said craft.

2. Steering mechanism for a dirigible craft having a control surface for changing the heading of said craft, said apparatus comprising: power means for operating the control surface; control means for starting and stopping said power means; means including a two part pickoif for operating said control means on relative displacement of said parts; a gyroscope for positioning one part of said pick-off; motor means for positioning said other pick-off part; a magnetic compass; an electrical differential for deriving a signal and having two mechanical positional inputs one responsive to relative movement of said craft and compass and the other responsive to the relative movement of said craft and motor means; and means for operating said motor means in accordance with the magnitude of said signal from said differential for nulling said differential through one mechanical input and relatively displacing said pick-off parts for maintaining the craft on a magnetic heading.

3. Heading control mechanism for an aircraft having a steering control surface, said apparatus comprising: a magnetic compass, an electrical differential device actuated by said compass for producing an electrical signal upon relative movement of said craft and compass, an amplifier operated by said signal, a, motor having a low rotation rate and connected to said amplifier and operatively connected to said differential for nulling said signal, a second signal producing device positioned by said motor, a signal responsive means including a second motor controlled from said secondsignal producing device, a free gyroscope rotated relative to said craft about an axis upon change in heading of said craft, a third signal producing device operatively connected to and responsive to the algebraic sum of the rotations of the gyroscope and second motor, a manually operable fourth signal producing device for changing craft heading at a selected rate, selectively operable means for rendering said signal responsive means and second motor non-responsive to said second signal producing device and responsive to the fourth signal producing device, a velocity signal generator in series with said fourth signal producing device for limiting the speed of the second motor to the magnitude of the fourth signal, power means for operating the control surface of the craft, means for controlling said power means from the third signal producing device, and means for maintaining the second signal producing device in a null condition during control of said signal responsive means and second motor from the fourth signal producing device to avoid sudden operation of said second motor upon subsequently rendering said signal responsive means and second motor responsive to said second signal device.

4. Heading control apparatus for an aircraft having a control surface for steering said craft, said apparatus comprising: a magnetic heading signal providing means comprising two relatively stationary interconnected members, a rotor associated with one member and rotatable relative thereto, and means for energizing the rotor in accordance with the changes in magnetic heading whereby signals proportional to change in heading are supplied to the rotor; signal responsive means including a motor having a shaft operatively connected to said rotor and controlled by said heading signal for driving said rotor to reduce the signal supplied to the rotor; a variable source of voltage having two relatively adjustable members for varying the magnitude of the voltage; means for relatively adjusting said members of said voltage source from said motor shaft; a first amplifier providing a fixed output signal and connected to be responsive to the variable voltage source; a second amplifier connected to the output of the first amplifier and responsive to the fixed signal; a second motor controlled from the second amplifier; a velocity signal generator driven by the second motor and connected to the second amplifier in opposition to the fixed signal to proportion the motor speed to the magnitude of the fixed signal; a second variable voltage source having two relatively displaceable members to vary the magnitude of the voltage produced thereby; means for relatively displacing the members of the second voltage source from the second motor; a gyroscope responsive to changes in craft heading for modifying the relative position of the adjustable members of said second variable voltage source; power means for operating said control surface; and means for controlling said power means from said second variable source of voltage, whereby upon changes in heading of said craft due to drift of said gyroscope said magnetic heading signal providing means returns said craft to said original heading at a rate dependent upon said fixed signal.

ROBERT J. KUTZILER.

(References on following page) 13 References Cited in the file of this patent Numb r UNITED STATES PATENTS 2:233:23; Number Name Date 2:614:335

1,436,280 Minorsky Nov. 21, 1922 5 1,958,258 Alexanderson May 8, 1934 2,387,795 Isserstedt Oct. 80, 1945 N b 2,439,701 Stuart Apr. 13. 1948 49,251 2,520,922 Framme et a1 Sept. 5, 1950 2,539,411 Osval et a1. Jan. 30, 1951 10 536,50

Name Date Douglas May 20, 1952 Glenny July 8, 1952 [Noxon Oct. 21, 1952 FOREIGN PATENTS Country Date France Nov. 12, 1938 (Addition to No. 793,301)

Great Britain Mar. 20, 1947 

